1. Field of the Invention
This invention relates to a method of manufacturing a microlens, more particularly to a method of manufacturing a microlens array.
2. Description of the Related Art
Since microlens arrays are used extensively in optoelectronic industries for applications related to flat panel display, optical communication coupling, and near-field optical storage technologies, the microlens array manufacturing technology has become one of the major industrial developments.
A conventional method of manufacturing a microlens array is disclosed in R.O.C. Publication No. 463058 entitled “Batch production of sphere microlens array,” and comprises the steps of: coating a first polymer onto a substrate; coating a second polymer onto the first polymer, wherein the first polymer has a glass transition temperature (Tg) greater than that of the second polymer; processing the first polymer and the second polymer by yellow light lithography to form two identical patterns on the first polymer and the second polymer; heating the substrate to a working temperature, wherein the working temperature is higher than the glass transition temperature of the second polymer and lower than the glass transition temperature of the first polymer for performing a reflow of the second polymer; maintaining the working temperature to adjust the appearance of the second polymer through a surface tension of the second polymer until the second polymer forms the shapes of sphere microlenses; and finally performing a cooling process to fixedly form the sphere microlenses. U.S. Pat. No. 5,298,366 for a “Method for Producing a Microlens Array” also implements a similar way of obtaining a microlens array.
Another conventional method of manufacturing a microlens array is disclosed in R.O.C. Pat. No. I289683 entitled “Manufacturing method of microlens arrays,” and comprises the steps of providing a mold layer with a plurality of grooves, a resin and a substrate; performing a material feeding process to feed the resin into the plurality of grooves of the mold layer; performing a transfer process to transfer the resin in the plurality of grooves onto the substrate, wherein the surface tension of the resin on the substrate forms a structure with a curved surface; and finally performing a solidification process to solidify the resin with the curved surface on the substrate and form the microlens array.
In general, the aforementioned conventional method of manufacturing a microlens array has the following drawbacks. The manufacturing processes disclosed in R.O.C. Pat. No. 463058 and U.S. Pat. No. 5,298,366 both require repeated exposures and photoresist removals over the substrate, and thus cannot manufacture microlenses in mass production continuously. The manufacturing efficiency is therefore very low. The manufacturing method still uses a developer used in the yellow light lithography for removing an unnecessary portion of the photoresist, causing a waste of the first polymer and the second polymer, and incurring a high manufacturing cost. Furthermore, the conventional manufacturing method can produce only microlenses of spherical lenses but not those of aspherical lenses with a high add-on value.
The manufacturing procedure disclosed in R.O.C. Pat. No. I289683 requires a step of turning the plurality of grooves of the mold layer upward to perform the material feeding procedure each time after the transfer procedure is completed. Such requirement reduces the overall efficiency of manufacturing the microlens substantially and increases inconvenience in the use of the mold layer. In addition, the conventional manufacturing method requires a LIGA electrocasting or laser etching method to manufacture the mold layer having the plurality of grooves in advance, and thus leads to inconvenience to the manufacture of the microlens. Both of the above-mentioned drawbacks increase the productions costs.
Moreover, regarding lens deformation caused by electric field, a method is disclosed in a US Pub. No. 2009/0027778, entitled“Deformable Optical Element, Methods of Making and Uses Thereof” A deformable optical element including an elastically deformable lens and electrical contacts directly attached to the elastically deformable lens is presented. A voltage can be applied to the electrical contacts, so as to deform the deformable optical element by forcing opposite sign charge onto the electrical contacts. However, this method can only be implemented by the fixedly attached electrical contacts for the voltage to apply to the deformable optical element, and it is obviously difficult to fixedly mount these electrical contacts onto the elastically deformable lens while the elastically deformable lens is tiny.
Obviously, the aforementioned conventional methods of manufacturing microlens arrays required improvements.